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M³ amplifier build discussions thread - Page 8  

post #106 of 828
3/11/05 at 8:07pm
Thread Starter 
Quote:
Originally Posted by Akku
If I don't want the bassboost option I just need to bridge across sbb. Right?
Yes.

Quote:
What the purpose of C2? Can I use some 1uF BG non polar caps I have laying in my drawer?
C2 is for improving the tracking between the N and P channel output devices at higher frequencies. I suggest using film caps here rather than electrolytics.

Quote:
Why polypropilene for C6? As long as they are PS bypass caps, why not cheaper polyester?
Polyester may not have good enough HF characteristics.
post #107 of 828
3/11/05 at 8:16pm
Thanks Morsel and AMB.
post #108 of 828
3/11/05 at 9:34pm
M³ assembled and running fine



Panasonic FM electrolytics, Wima MKS 4.7uF film, Vishay Dale 0.1% nonmagnetic resistors, 3x ad843kn, 2.5" heatsinks, matched mosfets (dc offset 2mV / 3mV), atm 80mA bias current, going to push it to 110mA, C1=10pF, polypropylene Orange Drops for bass boost



first thing I recognized was the easy deep black rocksolid bass overall sound is very easy with much detail. Even with "only" 30V and ad843's the M³ is driving my K1000 very fine (the HD600 anyway) I don't see any reason to go up to 36V or use opa604. Finally I found an amp to kick the ass of my K1000 :thumbsup

Unfortunately I'll be on the road tomorrow all day long, so intensive tests have to wait until Sunday.

Many thanks to Morsel and amb, you designed a great amp that really rocks
post #109 of 828
3/11/05 at 10:07pm
Thread Starter 
Cool steinchen, those tall heat sinks make the board look like a serious power plant .
post #110 of 828
3/11/05 at 10:45pm
Congrats on your amp, steinchen. Glad M³ is driving your K1000 well.

Quote:
Polyester may not have good enough HF characteristics.
I'm comfortable bypassing with polyester caps. They have a venerable history in the audio community for this very purpose. Having said that, if anyone finds conditions where polyester is insufficient, please let us know. In any case, using polypropylene isn't going to hurt. C2 and C8 don't have to be 1µF, .1µF is OK too, so you can use .1µF polypropylene for all the film caps except Cbb, which is better off with .22µF if you want a 20-80Hz bass boost range. So, my bottom line for C2, C6, & C8, .1-1µF polyester or polypropylene is all good, you don't have to follow our exact recommendations.
post #111 of 828
3/12/05 at 2:23am
Hi

I am going to use this mount kit. Do I need to apply thermal compound still or no? If so, where do I apply the thermal compound?

Also, where are you guys buying your hardware for mounting the heatsink to the board?

thanks in advance
post #112 of 828
3/12/05 at 7:21am
Thread Starter 
Quote:
Originally Posted by legodude
I am going to use this mount kit. Do I need to apply thermal compound still or no? If so, where do I apply the thermal compound?
Put the thermal compound on both sides of the insulator. You don't need to put a lot, just a thin film is enough. If you use too much goo, when the insulator is pressed down between the MOSFET and the heat sink, it will ooze out the side and make a mess.

Quote:
Also, where are you guys buying your hardware for mounting the heatsink to the board?
Your local hardware store should have what you need. Either use #4 self-tapping screws, or tap the holes on the heat sinks with a #4-40 tap about 1/2" deep, and then use #4-40 machine screws.
post #113 of 828
3/12/05 at 8:05am
The OnSemi Linear and switching voltage regulator handbook has a pretty decent guide for heastsinks and "goo" and other related stuffs.
There is a "better" one but I can't find it.


Quote:
Put the thermal compound on both sides of the insulator. You don't need to put a lot, just a thin film is enough. If you use too much goo, when the insulator is pressed down between the MOSFET and the heat sink, it will ooze out the side and make a mess.
Nice post.

I would add that it's usually a good idea to mount the MOSFET's to the heatsinks.....screw the heatsinks down and then solder them to the board so you are not stressing the leads.
post #114 of 828
3/12/05 at 9:20am
In this rightmark analyser loopback page, http://www.amb.org/audio/mmm/rmaa_mmm_v_loopback.html .

How much watt use when this measurement in perform?
post #115 of 828
3/12/05 at 10:31am
Quote:
Originally Posted by amb
Either use #4 self-tapping screws, or tap the holes on the heat sinks with a #4-40 tap about 1/2" deep, and then use #4-40 machine screws.
AMB, will the board (and the heatsinks) accept M3-screws (no pun intended )


/U.
post #116 of 828
3/12/05 at 1:16pm
Here's a link to the builds page of my completed M³:

http://www5.head-fi.org/forums/showt...42#post1287142
post #117 of 828
3/12/05 at 1:38pm
Very nice amp Thrice.
post #118 of 828
3/12/05 at 2:45pm
Thread Starter 
Quote:
Originally Posted by Nisbeth
AMB, will the board (and the heatsinks) accept M3-screws (no pun intended )
Yes it will.
post #119 of 828
3/12/05 at 2:51pm
Thread Starter 
Quote:
Originally Posted by jasonhanjk
In this rightmark analyser loopback page, http://www.amb.org/audio/mmm/rmaa_mmm_v_loopback.html .

How much watt use when this measurement in perform?
It's whatever the RMAA software does. If you're not familiar with the RMAA software, you simply press a button and it performs a series of tests automatically, analyzes the data and displays the results. I don't know specifically what output level it performs each tests in, and it's difficult for me to measure them because the test tones are complex and short in duration, but I'm sure it's nowhere near full output.
post #120 of 828
3/12/05 at 5:21pm
hi

I have one more question. In case I put a lot of thermal compound and it goos out on the sides, is it going to conduct through it?
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